JP4406876B2 - Ion exchange resin performance evaluation method and water treatment system management method - Google Patents

Description

The present invention is a method for evaluating performance of an ion exchange resins, and determines the replacement timing of the ion exchange resins, on how to manage the water treatment system for determining.

  Ion exchangers are widely used for purposes such as substance purification. For example, synthetic zeolite, which is an inorganic ion exchanger, softens water, ion exchange membranes concentrate and remove electrolytes by electrodialysis, salt production by seawater concentration, sugar solution purification, use in fuel cells, and ion exchange resins are water. It is used for treatment, wastewater treatment, food production, separation and purification of pharmaceuticals, wet scouring, analysis, and use as a catalyst.

  In particular, ion exchange resins are used in many fields including thermal power plants, nuclear power plants, semiconductor manufacturing plants, and general industrial plants. Specifically, ion exchange resins are used in make-up water treatment equipment, condensate demineralization equipment, etc. in thermal power plants and nuclear power plants, and are usually mixed bed type of cation exchange resin and anion exchange resin. It is used. In the makeup water treatment apparatus, ion components and the like in raw water are removed by ion exchange resin to produce pure water having an electric conductivity of 1 μS / cm or less and replenished to power plant system water. The condensate demineralizer removes ionic components in condensate and corrosion products generated from plant components, and also removes seawater components when seawater used as condenser cooling water leaks. An ion exchange resin is used for the purpose, and advanced condensate treatment that achieves an electric conductivity of 0.1 μS / cm or less is required.

  In semiconductor manufacturing factories, ion exchange resins are used in production facilities for ultrapure water used in the cleaning process for LSI chips and the like, and with an increase in the degree of integration of semiconductors, the specific resistivity is 18 MΩcm or more and the ion concentration is increased. It is required to produce ultrapure water below the ppt level.

  In general industrial plants, ion-exchange resins are used in pure water production equipment, which is usually a mixed-bed type. In addition, decolorization and desalination of starch sugar and sucrose, recovery of metals in chemical processes, and purification of chemical products It is also widely used as an acid-base solid catalyst for organic chemical reactions.

  As described above, although it is an ion exchange resin used in various fields, its performance may be deteriorated due to organic substances in raw water used, impurities in system water, contact between resins, and the like. Normally, the performance of the ion exchange resin (ion exchange capacity) can be recovered by a regeneration operation using acid or alkali, etc., but if the impurities are irreversibly adsorbed to the ion exchange resin, the above regeneration is performed. It is difficult to restore performance by operation. Therefore, the ion exchange resin whose performance cannot be recovered by the regeneration operation needs to be replaced.

  In the case of an ion exchange resin used in a mixed bed type, the reaction rate of the ion exchange resin having one charge code may be significantly reduced. This is considered to be caused by, for example, when the ion exchange resin is subjected to oxidative degradation or the like, part of the ion exchange resin is eluted or peeled off and adsorbed on the ion exchange resin having the opposite charge sign. Yes. In addition to the adsorption of the eluate and exfoliation from the ion exchange resin having the opposite charge sign, the influence of impurities in the water is also considered, and the evaluation of the reaction rate of each ion exchange resin is not sufficient. The cause of deterioration cannot be fully understood, and water quality management cannot be performed correctly.

  By the way, it is clear that the reaction rate (for example, mass transfer coefficient: MTC) of the anion exchange resin is lowered due to the influence of the cation exchange resin for the ion exchange resin used in the condensate demineralizer of the power plant. It has become. That is, the cation exchange resin undergoes oxidative decomposition under the influence of catalytic action of metal ions such as Fe ions and Cu ions in water and dissolved oxygen, and polystyrene sulfonic acid (hereinafter referred to as “PSS”), which is the base structure of the cation exchange resin. Are eluted and adsorbed and contaminated on the surface of the anion exchange resin, reducing the reaction rate of the anion exchange resin. In general water treatment equipment such as pure water production equipment, the anion exchange resin affects the cation exchange resin, contrary to the phenomenon of the condensate desalination equipment at the power plant. This also causes a phenomenon that the reaction rate decreases.

  In an actual plant, the reaction rate of the anion exchange resin does not necessarily decrease gradually with the period of use, but it suddenly decreases from a certain period of time. Therefore, simply measuring the reaction rate of the anion exchange resin makes it possible to perform anion exchange. It is not possible to predict when to replace the resin. In this way, performance evaluation management of ion exchange resin based on reaction rate alone is not sufficient for water quality management, and more appropriate performance evaluation of cation exchange resin and anion exchange resin, prediction of replacement time, and determination of replacement time are important. It is coming.

The present inventors perform surface analysis of the anion exchange resin, measure the amount of PSS adsorbed on the surface, evaluate the performance of the anion exchange resin and predict the replacement time, and replace the anion exchange resin. A method for determining the timing was devised.
JP-A-10-267838

  This method is superior to the conventional evaluation method based on the reaction rate, but the effect of PSS adsorbed on the surface of the anion exchange resin on the resin differs depending on the molecular weight. It was necessary to accumulate data.

The present invention eliminates the problems of the prior art as described above, and provides an efficient and simple method for evaluating the performance of an ion exchange resin , and an efficient and simple water treatment for determining and determining the replacement time of an ion exchange resin. It is intended to provide a system management method.

The present invention measures the interaction between the cantilever and the ion exchange resin surface is a tip of an atomic force microscope, check the status of the charges on the surface of the ion exchange resin, the performance evaluation of an ion exchange resin An ion exchange resin performance evaluation method characterized by the above is provided. Particularly suitable ion exchange resins for applying this method are cation exchange resins used in mixed bed systems, anion exchange resins used in mixed bed systems, and condensate demineralizers at power plants. An anion exchange resin used, a cation exchange resin or an anion exchange resin used in a pure water production apparatus. Here, our method of Ru examine the state of the surface charge is a method of using an atomic force microscope, the interaction with specific, the cantilever and the ion exchange resin surface is a tip of an atomic force microscope This is a method for measuring and examining the state of the charge on the surface of the ion exchange resin , whereby the performance of the ion exchange resin can be evaluated.

Further, the present invention performs a performance evaluation of the ion exchange resin by the performance evaluation method of the ion exchange resin, to predict the reaction rate decline since of the ion-exchange resin, to determine the replacement timing of the ion exchange resin The management method of the water treatment system characterized by this is also provided.

Generally, when evaluating the surface charge of a substance, the zeta potential is measured. Electrophoresis can also be used for fine particle ion exchangers that can be dispersed in a liquid, but granular ion exchange resins are not applicable because they are not dispersed in a liquid. Streaming potential method can also be used for membrane and fibrous ion exchangers. However, it is difficult to apply if the surface of the ion exchanger does not generate a potential because the ions permeate inside the ion exchanger. It is considered that the resin is difficult to apply due to macroscopic unevenness. Therefore, in the case of the granular ion exchange resin according to the present invention , the interaction between the atomic force microscopy (AFM) probe (cantilever) and the resin surface is measured, and the state of charge on the resin surface is evaluated. how to take.

Conventionally, in order to maintain the quality of water in the circulation system of a power plant in good condition, it is necessary to keep the ion exchange resin in the condensate demineralization tower of the condensate demineralizer healthy. Further, the same applies for other general water treatment device, such as pure water production system (demineralizer), it is important for water quality management is possible to accurately evaluate and determine ion exchange resins of performance in either case . Incidentally, in Examples described below, the reaction rate (e.g., mass transfer coefficient: MTC) of ion exchange resin from the charge to a good correlation was found of the resin surface, the method of the present invention the performance evaluation of an ion exchange resin It was found to be effective. Therefore, according to the management method of the water treatment system of the present invention performs a performance evaluation of the ion exchange resin by examining the charge of the ion exchange resin surface, to predict its lifetime, to determine the replacement timing of the ion exchange resin Is possible. In addition, the method of the present invention is much simpler than the reaction rate measurement method such as the MTC measurement method, and is also simpler than, for example, the surface analysis method that needs to accumulate data for each molecular weight of PSS.

Hereinafter, as the best mode for carrying out the invention, an aspect of measuring the interaction between the probe of the atomic force microscope (cantilever) and the surface of the ion exchange resin and examining the state of charge on the resin surface will be described. The present invention is not limited to these .

The interaction (attraction, repulsion) between the cantilever charged in the liquid and the surface of the ion exchange resin is measured, and the state of charge on the surface of the ion exchange resin is evaluated. As the cantilever, for example, those made of Si or Si ₃ N ₄ are generally used, but are not limited to these as long as they are charged in the liquid.

  In addition, since the tip diameter of the cantilever is as thin as several nanometers, data variations are likely to occur due to the local structure of the surface of the ion exchange resin, so that particles of several tens of μm are fixed to the tip of the cantilever. By measuring the interaction between the particle surface and the surface of the ion exchange resin, the interaction between the cantilever and the surface of the ion exchanger can be measured with high sensitivity. Examples of the particles to be fixed include glass particles such as glass spheres, silica particles, polymer particles, metal particles, and particles whose surface is modified with an ionic functional group, and are charged in a liquid. Any material can be used.

  In carrying out the method for managing a water treatment system according to the present invention, the surface charge state of the ion exchange resin as described above (the charged cantilever [the particle may be fixed at the tip]) and the surface of the ion exchange resin It is necessary to grasp in advance the correlation between the measurement / evaluation result of the action) and the reaction rate of the ion exchange resin. Using this correlation, the anion exchange resin and cation used in the actual water treatment system such as a condensate demineralizer and a pure water production device can be obtained from the evaluation result of the surface charge state of the ion exchange resin. Predict and determine the replacement time of ion exchange resins such as exchange resins.

  For example, the reaction rate of the ion exchange resin is measured by the method of measuring the ion exchange rate by measuring the specific resistance at the column outlet in Example 1 described later, the shallow bed method, the mass transfer coefficient “MTC” (mass transfer coefficient) It can be performed by a known method such as a method by measurement. The shallow bed method is a method in which a salt-containing water such as NaCl or sodium sulfate is passed through an ion exchange resin layer having a resin layer height of about 10 mm and the ion removal rate is measured. On the other hand, a method by measurement of a mass transfer coefficient “MTC” is usually used, and an outline of an example of the measurement method is as follows.

For example, an anion exchange resin sampled from a condensate demineralizer at a power plant is regenerated using NaOH, and the regenerated resin and the H form of a new cation exchange resin are regenerated anion exchange resin / cation exchange resin capacity. Mix at ratio = 1/2 and load into column. Next, ammonium ions (ammonia water) and sodium sulfate are passed through the upper part of the column in the form of an aqueous solution having a predetermined concentration at a flow rate of 70 L / hr (liter / hour). Column inlet water and outlet water are collected in the water flow, and the sulfate ion concentration is measured. After the water flow is completed, the porosity and the anion exchange resin particle size are measured. The mass transfer coefficient “MTC” is calculated according to the following “Equation 1”. It can be said that the higher the value, the higher the reaction rate of the anion exchange resin and the sounder the performance. Usually, the MTC value of a new anion exchange resin is about 2.0 (× 10 ⁻⁴ m / sec).

但し、
Ｋ：物質移動係数「ＭＴＣ」（ｍ／ｓｅｃ）、ε：空隙率、Ｒ：陰イオン交換樹脂／全イオン交換樹脂容量比、Ｆ：通水流量（ｍ³ ／ｓｅｃ）、Ａ：樹脂層断面積（ｍ² ）、Ｌ：樹脂層高（ｍ）、従ってＡ×Ｌ：樹脂量（ｍ³ ）、ｄ：樹脂粒径（ｍ）、Ｃ₀ ：入口水のＳＯ₄ ^2- 濃度、Ｃ：出口水のＳＯ₄ ^2- 濃度。

However,
K: Mass transfer coefficient “MTC” (m / sec), ε: Porosity, R: Anion exchange resin / total ion exchange resin volume ratio, F: Water flow rate (m ³ / sec), A: Resin layer breakage Area (m ² ), L: Resin layer height (m), therefore A × L: Resin amount (m ³ ), d: Resin particle size (m), C ₀ : SO ₄ ²⁻ concentration of inlet water, C: SO ₄ ^2- concentration of outlet water.

The reaction rate is low when the MTC is low, and the general exchange time of the anion exchange resin is, for example, when MTC = 1 (× 10 ⁻⁴ m / sec). Whether the anion exchange resin should be replaced at this point depends on the operating conditions of the apparatus and the required performance of the water quality, and should be determined individually and specifically. Using the MTC value determined in each case as a reference, the anion exchange resin replacement time is determined based on the comparison between the evaluation result of the surface charge state of the anion exchange resin and the MTC correlation in each case. Can be predicted and determined.

  The following examples further illustrate the present invention, but the present invention is not limited thereto.

  Collecting resin from MB tower (mixed bed ion-exchange tower) whose water quality has deteriorated using a mixed-bed pure water production system at a semiconductor manufacturing plant, and measuring the reaction rate and the interaction between the cantilever and the resin surface in an atomic force microscope did. The collected resins were a strongly acidic cation exchange resin Amberlite IR124 manufactured by Rohm and Haas and a strongly basic anion exchange resin Amberlite IRA402BL manufactured by Rohm and Haas.

The reaction rate was compared by the ion exchange rate. The ion exchange rate was evaluated by passing an aqueous salt solution at a constant concentration through the ion exchange resin, gradually increasing the linear velocity (LV), and measuring the specific resistance at the outlet at that time. Specifically, in the case of an actual measurement sample of a cation exchange resin, 30 ml of this sample and 70 ml of a new anion exchange resin Amberlite IRA402BL are packed into a column as a mixed bed, and a NaCl aqueous solution equivalent to 15 μS / cm is added to the column. The solution was passed through the column. The results are shown in Table 1. In the case of an actual measurement sample of an anion exchange resin, 30 ml of this sample and 70 ml of a new cation exchange resin Amberlite IR124 are packed into a column as a mixed bed, and a Na ₂ SO ₄ aqueous solution equivalent to 15 μS / cm is applied to the column. The liquid was passed. The results are shown in Table 2. In addition, for comparison, in each of the above cases, a new bed of ion exchange resin is used instead of the actual measurement sample to form a mixed bed, and each salt solution is passed through each column. The specific resistance was measured. These results are also shown in Tables 1 and 2, and are data indicated as “new” in the column of “specific resistance at outlet”. In Tables 1 and 2, it is shown that liquid was sequentially passed from the upper stage toward the lower stage. Taking Table 1 as an example, ultrapure water was passed at LV = 20 m / hr for 20 minutes, then NaCl aqueous solution was passed at LV = 20 m / hr for 5 minutes, and then NaCl aqueous solution was passed at LV = 30 m / hr. It shows that the solution was passed for 5 minutes, and finally the NaCl aqueous solution was passed for 5 minutes at LV = 40 m / hr.

  In the case of a new measurement sample of the cation exchange resin Amberlite IR124, the specific resistance is hardly changed even if the LV is increased, but in the case of the actual measurement sample, the specific resistance is decreased if the LV is increased. Indicates that it is decreasing. In the case of the anion exchange resin Amberlite IRA402BL, in either the new measurement sample or the actual machine measurement sample, the specific resistance hardly changed even when the LV was increased, and the specific resistance did not substantially decrease even in the actual machine measurement sample. It can be seen that the reaction rate has hardly decreased.

The interaction between the cantilever and the resin surface in the atomic force microscope was measured under the following conditions.
[Measurement condition]
-Apparatus: Atomic force microscope SPA-400 (manufactured by Seiko Instruments Inc.)
Cantilever: SN-FF01, Si ₃ N ₄ made, spring constant 0.06 N / m (manufactured by Seiko Instruments Inc.)
・ Measurement solution: pH 3 (adjusted with HCl)
・ Measurement mode: Force curve measurement

  FIG. 1 shows the measurement of the interaction between the cantilever and the resin surface for the new measurement sample and the actual measurement sample of the cation exchange resin Amberlite IR124, and FIG. Results are shown. In both figures, the horizontal axis represents the distance between the cantilever and the resin surface, and the vertical axis represents the force received by the cantilever. The results of “reaction rate” in Tables 1 and 2 and FIGS. 1 and 2 and “interaction (force between surfaces)” between the cantilever and the resin surface in an atomic force microscope are summarized in Table 3.

It is known that Si ₃ N ₄ is positively charged in a pH 3 solution.
“Ultra-precision wafer surface control technology” p. 237, Science Forum Inc.

  In the case of a new measurement sample of the cation exchange resin Amberlite IR124, an attractive force is detected, indicating that the resin surface is negatively charged. In the cation exchange resin amberlite IR124 whose performance in the case of an actual machine measurement sample has been reduced, no attractive force is detected, indicating that the charge on the resin surface is almost neutralized. On the other hand, in the case of the anion exchange resin Amberlite IRA402BL, the repulsive force was detected both in the case of the new measurement sample and the actual measurement sample, indicating that the resin surface was positive and not changed and the performance was not deteriorated.

  Since there was a correlation between the reaction rate of the ion exchange resin and the charge on the surface, the performance evaluation method of the ion exchanger of the present invention (in this example, the interaction between the cantilever and the resin surface in the atomic force microscope was measured. Is effective for the evaluation of ion exchange resins. The reaction rate measurement test in this example requires 100 ml as the amount of ion exchange resin and requires several tens of minutes, but in the measurement of this example according to the present invention, in principle, measurement can be performed with one resin particle. Since the time is several seconds per measurement, the performance of the resin can be evaluated very efficiently and simply.

Adsorption of 0 to 298 mg of PSS (manufactured by Tosoh Corporation) with an average molecular weight of 10,000 and 1,000,000 per 1 liter of resin is applied to the strongly basic anion exchange resin Amberlite IRA900CP manufactured by Rohm and Haas. The resin used (hereinafter, expressed in units of PSS adsorption amount: mg / LR) was used as a measurement sample. For each resin measurement sample, the mass transfer coefficient (MTC) and the interaction between the particle-fixed cantilever and the resin surface in an atomic force microscope were measured. The particle-fixed cantilever is obtained by fixing a glass sphere having a radius of about 20 μm as a particle to the tip of a Si ₃ N ₄ cantilever and measuring the interaction between the glass sphere and the resin surface.

The interaction between the glass sphere at the tip of the cantilever and the resin surface in the atomic force microscope was measured under the following conditions.
[Measurement condition]
-Apparatus: Atomic force microscope SPA-400 (manufactured by Seiko Instruments Inc.)
Cantilever: SN-FF01, made of Si ₃ N ₄ , spring constant 0.9 N / m (manufactured by Seiko Instruments Inc.)
・ Measurement liquid: Ultrapure water ・ Measurement mode: Force curve measurement

  FIG. 3 shows the measurement results of the interaction between the glass sphere at the tip of the cantilever and the resin surface of the resin obtained by adsorbing 0 to 298 mg / LR of PSS having an average molecular weight of 10,000 on the anion exchange resin Amberlite IRA900CP. The horizontal axis (x-axis) is the distance between the glass sphere surface and the resin surface, and the vertical axis (y-axis) is the force received by the cantilever. In the case of 0 mg / LR that does not adsorb PSS, the attractive force is detected. As the adsorption amount of PSS increases, the magnitude of the attractive force decreases. In the case of the PSS adsorption amount of 298 mg / LR, the repulsive force is detected. Has been. Since the glass is negatively charged in neutral water, the surface of the anion exchange resin Amberlite IRA900CP is positively charged, indicating that the charge is shifted in the negative direction as the PSS adsorption amount increases. .

  Table 4 shows the results of measuring the interaction between the glass sphere at the tip of the cantilever and the resin surface (force between the surfaces) and the mass transfer coefficient (MTC) for the resins adsorbed with molecular weights of 10,000 and 1,000,000, respectively. ) Shows the measurement results. When attraction is detected, the minimum value of the y-axis is used, and when repulsive force is detected, the y value at x = 0 is used as an index. At any molecular weight, MTC is below the value of 1.0 which is a general exchange standard for anion exchange resins when changing from attractive force to repulsive force. On the other hand, the PSS adsorption amount at this time varies depending on the molecular weight. Further, while the MTC changes rapidly, the magnitude of the attractive force (that is, the state of charge on the surface) gradually decreases (that is, the state of charge changes in the negative direction). From the above, it was found that the time when the MTC decreases can be predicted by measuring the surface charge state.

Resin collected over time after a certain period of time was used as a measurement sample of the strongly basic anion exchange resin Amberlite IRA900CP used in the condensate demineralizer at power plants A and B. Needless to say, the anion exchange resin and the cation exchange resin used in the condensate demineralizer are periodically regenerated. For each measurement sample, the mass transfer coefficient (MTC) and the interaction between the particle-fixed cantilever and the resin surface in an atomic force microscope were measured. The particle-fixed cantilever is obtained by fixing a glass sphere having a radius of about 20 μm as a particle to the tip of a Si ₃ N ₄ cantilever and measuring the interaction between the glass sphere and the resin surface. The measurement conditions for the interaction between the glass sphere at the tip of the cantilever and the resin surface in the atomic force microscope (force between the surfaces) were the same as in Example 2. The results are shown in Table 5. In Table 5, the uppermost stage of the data is for the initial stage of resin use, the resin usage period becomes longer toward the lower stage, and the lowermost stage of the data is for the late stage of resin use. In Table 5, the PSS adsorption amount was determined by Fourier transform infrared total reflection spectroscopy.

  In the power plant A, the PSS adsorption amount increases to 155 mg in the latter period of use, but the force between the surfaces remains attractive (that is, the charge on the resin surface is positive), and the MTC is not greatly reduced. On the other hand, in the power plant B, when the PSS adsorption amount increases to 159 mg, which is almost the same as that in the power plant A, the force between the surfaces changes to repulsive force (that is, the charge on the resin surface changes to minus), and MTC is Decrease significantly. From the above results, it was found that the time when the MTC decreases can be predicted by measuring the surface charge state.

  Since a good correlation was observed between the charge on the surface of the resin and the MTC, it was found that by examining the charge on the surface of the resin, it is possible to evaluate the performance of the resin, predict the lifetime, and determine the replacement time. The surface charge measurement method using AFM is different in the magnitude of the force acting between the surfaces depending on the material of the cantilever to be used, the spring constant, and the material and size of the particle to be fixed when fixing the particle to the cantilever. It will also be appreciated that the relationship between the change in force between the surfaces and performance must be examined in advance.

According to the performance evaluation method of an ion exchange resin of the present invention, it is possible to accurately evaluate and determine ion exchange resins performance. Further, according to the management method of the water treatment system of the present invention, to predict the usage limit before the ion-exchange resin in Japanese may not function properly, the water treatment system can be stably managed. Therefore, the method of the present invention includes, for example, water treatment devices in many fields including semiconductor manufacturing plants and general industrial plants, such as makeup water treatment devices and condensate demineralization devices in thermal power plants and nuclear power plants, It can be used in wastewater treatment equipment, pure water production equipment, etc., and particularly preferably, determination of the replacement time of anion exchange resin used in condensate demineralization equipment for PWR and BWR nuclear power plants, etc. Can be applied to.

FIG. 1 is a graph showing, as a force-distance curve, a measurement result of an interaction between a cantilever and a resin surface in an atomic force microscope for a new measurement sample and an actual measurement sample of a cation exchange resin. FIG. 2 is a graph showing, as a force-distance curve, measurement results of the interaction between the cantilever and the resin surface in an atomic force microscope for a new measurement sample and an actual measurement sample of an anion exchange resin. FIG. 3 shows the interaction between a glass sphere fixed to the tip of a cantilever and the resin surface in an atomic force microscope for a resin obtained by adsorbing 0 to 298 mg / LR of PSS having an average molecular weight of 10,000 on an anion exchange resin. It is a graph which shows a measurement result as a force-distance curve.

Claims (4)

Measuring the interaction of the atomic force microscope probe is a cantilever and the ion exchange resin surface, examines the state of charge of the surface of the ion-exchange resin, and performing performance evaluation of the ion exchange resin Ion exchange resin performance evaluation method. The ion exchange resin performance evaluation method according to claim 1, wherein the ion exchange resin is a cation exchange resin or an anion exchange resin used in a mixed bed type. The ion exchange resin is an anion exchange resin used in a condensate desalination apparatus of a power plant, or a cation exchange resin or an anion exchange resin used in a pure water production apparatus. A method for evaluating the performance of the ion exchange resin according to claim 1 or 2. The performance evaluation method of an ion exchange resin according to any one of claims 1 to 3 The performance evaluation of the ion exchange resin, to predict the reaction rate decline since of the ion exchange resin, the replacement timing of the ion exchange resin A method for managing a water treatment system, characterized by deciding.

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